This invention relates to a bevel gear cutting device. In any one of bevel gears, the teeth on the gear converge towards the virtual apex of the conical shape of the gear and continuously increase their cross-section areas from the end adjacent to the virtual apex or the smaller diameter end towards and to the end opposite to the virtual apex or the larger diameter end of the gear. Therefore, hithertofore, the bevel gear cutting operation has encountered many difficulties. In prior art bevel gear cutting methods, the following three types of methods have been known, that is, the template method, the formed method and the generating method as in the case of the spur gear cutting. However, the template method has been most commonly employed and this bevel gear cutting method is generally classified into the profiling system, the Bilgram system, the Reinecker system and the Gleason system.
In the template type bevel gear cutting device utilizing the profiling system, the template is mounted on a bevel gear blank in a position spaced from the virtual apex of the conical shape of the gear blank making the best use of the shape of a straight bevel gear and the cutter is linearly and reciprocally moved along the template between the virtual apex of the bevel gear blank and the template so that the cutter is always directed towards the apex of the pitch cone of the bevel gear blank to thereby cut the teeth on the bevel gear blank one tooth at a time. However, the cutting efficiency of the profiling system of the template method is low and there is the inconvenience that the template has to be changed each time a particular bevel gear is cut.
On the other hand, the bevel gear cutting device utilizing the Bilgram or Reinecker system is designed to position a bevel gear blank so that the gear blank will roll in engagement with a virtual crown gear and the gear blank has movement imparted thereto so that the blank rolls on the virtual crown gear with respect to the cutter which represents one surface of the teeth of the virtual crown gear on the opposite side of the shaft on which the gear blank is mounted to thereby cut teeth on the gear blank. Therefore, in the bevel gear cutting device based on the Bilgram or Reinecker system, the gear tooth has to be first finished on one surface and then on the other surface by changing the orientation of the cutter and therefore, the cutting efficiency of the gear cutting device is very low and it is difficult to cut the teeth on the gear blank with precision.
In the profiling bevel gear cutting device utilizing the Gleason system, a straight cutter representing the left- and right-hand surfaces of a virtual crown gear is reciprocally moved on a rocking plate which imparts rocking movement to the crown gear and the gear blank is rotated in proper engagement with the crown gear so as to cut teeth on the gear blank one tooth at a time to thereby provide an involute profile by the generating tooth cutting method. Thus, the Gleason system is higher in operation efficiency and precision than the above-mentioned profiling system, but since the tooth cutting is effected by reciprocally moving the cutter as in the case of the profiling system, the Gleason system cannot improve the cutting efficiency substantially. Also since the Gleason system cuts teeth on a gear blank intermittently instead of continuously by a rotating hob, the Gleason system cannot obtain a smooth involute curve.